This study aimed to explore the associations between TB transmission and socio-economic risk factors in a high TB and HIV burdened setting.

Background

Several studies have assessed the associations between biological factors and tuberculosis (TB) transmission. However, our understanding of the associations between TB transmission and socio-economic factors remains incomplete.

Methods

We conducted a cross-sectional molecular epidemiology study was among adult TB patients in a high TB/HIV burden community in Cape Town, South Africa. Demographic and clinical data were extracted from TB registers and clinical folders. Socio-economic data were collected using interviewer-administered questionnaires. M.tb isolates from participants were analysed using IS6110-based Restriction Fragment Length Polymorphism. Data were analysed using Stata Corp version 12 software. Composite “social” and “economic” scores were generated from social and economic variables obtained by interviewer-administered questionnaire.

Results

Of the 509 TB patients, 352 (69%) occurred in RFLP-defined clusters and 157 (31%) were “un-clustered”. Clustered cases were more likely to have lived longer in the study community, (adjusted odds ratio [aOR]= 1.06, 95% Confidence interval [CI]: 1.02-1.10, p=0.006) and in the same house (OR=1.04, C.I: 0.99-1.08, p=0.06); and had increased household crowding conditions (OR=0.45, C.I: 0.22-0.96, p=0.038). Also notable in this study was a trend towards lower economic score in the clustered group (OR=0.69, CI: 0.45-1.06, p-value=0.09).

Conclusions

Our study findings points to increased social interaction, poorer economic conditions and prolonged residence in a high burdened community being potentially important factors linked to TB transmission. While the association between poverty and TB transmission is not new, the importance of degrees of poverty within low socio-economic setting is novel. Our findings further suggest that even within low socio-economic settings, individuals at the lower end of the economic scale tend to be at greater risk of acquiring recently transmitted TB.